A known tire construction uses a body ply having reinforcement elements that extend from bead portion to bead portion through opposing sidewall portions, and a crown portion of the tire. Sometimes referred to as the carcass ply or reinforcing ply, the body ply is typically anchored at the beads and maintains the overall shape of the tire as the tire is inflated and used. The reinforcement elements of the body ply are usually oriented substantially along the radial direction (a direction perpendicular to the axis of rotation) and can include e.g., a ferrous metal.
During use of the tire, these reinforcement elements (sometimes referred to as cords) may be damaged e.g., from impact with objects in the roadway, travel over curbs, and other damaging events. In some situations, the reinforcement elements may be completely broken as a result of such an event. Unfortunately, this damage may not be readily discoverable from a visual inspection of the exterior of the tire because the reinforcement elements are contained within the rubber materials used to construct the tire.
Commercial tires are commonly reused after a process referred to as retreading. With retreading, worn tread is removed from the tire and a new tread belt or tread section is installed onto the tire. Replacement of the tread is less expensive than replacing the whole tire and allows additional mileage to be obtained using the same tire carcass. This practice is common particularly with commercial tires for heavy trucks.
Before replacing the tread, however, it is advantageous to inspect the tire, including the reinforcement elements of the body ply, for damage or wear. In certain situations, inspection may reveal that replacement of the tire is required rather than retreading. Alternatively, repair of the tire may be required. As stated above, not all damage to interior elements such as e.g., the reinforcement elements of the body ply are readily apparent from a visual inspection alone.
As the reinforcement elements in the body plies for commercial tires such as e.g., heavy truck tires are frequently constructed from a ferrous material, one or more sensors can be used to detect discontinuities in the reinforcement elements such as e.g., breaks that are not otherwise ascertainable from a visual inspection of the tire. It is desirable to automate such an inspection process so that multiple tires may be inspected economically and expediently. However, tires come in a variety of shapes and sizes. More specifically, the profile, height, and width (along the axial direction) can vary substantially from tire to tire. For tire inspection, some sensors require placement at an inner surface of the tire either in contact with the tire or in close proximity thereto. This can be problematic with tire profile and size changes from tire to tire.
Additionally, complexities can be encountered in the detection of discontinuities at certain locations of the tire. For example, the placement of certain sensors in the shoulder portion of the tire along the inner surface can be particularly challenging because the curvature at this portion of the tire and its variability between tires of different sizes and types. More particularly, challenges exist with accurately and consistently positioning one or more sensors at the inner surface of the tire, particularly at the shoulder region, over a range of tire profiles and widths so as to detect e.g., damage to the reinforcement elements of the body ply. In addition, it is preferable that the sensor or sensors are readily removable for use in inspecting another tire.
By way of additional example, detecting damage to the reinforcement elements of the body ply along the bead portion of the tire is also problematic. Each opposing bead portion of the tire typically includes a bead that extends along the circumferential direction forming a hoop or ring. This bead is constructed of ferrous metal that can interfere with accurate detection of damage to the reinforcement elements of the body ply near the bead portion of the tire. More specifically, the bead provides a substantial amount of ferrous metal that impedes the level of saturation of the reinforcement elements with magnetic flux that is desired for break detection. Some tire constructions also use a body ply that is wrapped around the bead, which further increases the amount of ferrous metal in the area where inspection is desired. Additionally, the non-linear geometry of the bead portion also impedes efforts to place the sensors close to the surface of the tire, which is desired for improved detection sensitivity and accuracy. The non-linear geometry and presence of ferrous metal also creates problems in creating fields of magnetic flux that are properly positioned at a level sufficient for damage detection but without undesirably saturating sensors used to detect the magnetic flux.
Vibrations during inspection can also cause problems. More particularly, in order to detect breaks over the entire circumference of the tire, the sensors may be passed over the surface of the tire along the circumferential direction by e.g., rotating the tire relative to the sensor. The interior surface of the tire is rough and unpredictable between different tires and different manufacturers. During movement of the sensor relative to the surface of the tire, the sensor will be bounced or otherwise mechanically agitated. A change in distance between the sensor and the tire will cause a change in the output signal from the sensor. In turn, this can cause false detections and missed detections. Reducing the sensitivity of the sensor to avoid false detections will also reduce the sensor's ability to detect breaks. Algorithms may be used to assist in filtering noise from the signal but such algorithms may be based on assumptions that could also reduce the sensor's ability to detect breaks.
Accordingly, a method of using a device that can be properly positioned along an inner surface of the tire to facilitate inspection of the tire for e.g., breaks or discontinuities in its reinforcements would be useful. Such a method that can also be used to compensate or correct sensor signals that are undesirably based on vibration or mechanical agitation would be particularly useful. Such a method that can be used with a device positionable along the inner surface of various tires at the shoulder regions or bead portions over a range of different tire profiles and widths would also be useful.